saxony



UNITED STATES PATENT OFFICE;

GERHARD SCHREIBER, OF GHEMNITZ, SAXONY, GERMANY, ASSIGNOR TO DIEDIRECTION DER PATENTPAPIERFABRIK ZU PENIG, OF PENIG, SAXONY.

PROCESS OF MANUFACTURING SAFETY-PAPER FOR CHECKS, 80C.

SPECIFICATION forming part of Letters Patent 0. 322,130, dated July 14-,1885.

Application filed March 16, 1885. (No specimens.)

Be it known that I, GERHARD SOHREIBER,

doctor of philosophy and chemist, a resident of the city of Ohemnitz, inthe Kingdom of Saxony, and German Empire, have invented a certain newand useful Improvement in the Process of Manufacturing Safety-Paper forChecks, &c., of which the following is a specification.

This invention relates to the manufacture of paper that shall at onceindicate anyalteration effected by chemical means of writing or othermarks made thereon. The known methods for the production of suchsafety-paper either do not offer perfect security for the purposerequired, on account of the chemical reagents employed therein, or theyare of such a complicated nature as not to be practically available.According to the present invention the purpose aimed at is attained bymanufacturing a colored paper of such a nature that the chemicalsemployed for removing writing or other marks in ink from the same, suchas acids, chlorine, &c., will destroy or alter the color, the paper thusafiording the required safety, as any attempt to remove or alter thewriting will at once become visible thereon. The requisite operationsfor the preparation of such paper are at the same time very simple anddo not affect or complicate the ordinary process of manufacturing paper,as

the requisite chemicals need only be added to the paper material in therag-engine.

The invention is carried out in practice as follows: The paper materialis colored with indigo, preferably with indigo from the steeping-vat orsteeping-trough, and is mixed with a chromate that is insoluble in waterand soluble in acidssuch as chromate of barium. The extent to which thelatter is added depends upon the degree of blue-green to yellow-greencoloration of the paper desired. On

paper so prepared dilute mineral acids effect wherein the papermaterial, after being 001- ored with indigo, is treated with chromatesinsoluble in water, but soluble in alcohol.

In testimony whereof I have signed my name to this specification in thepresence of two sub-.

scribing witnesses.

GERHARD SGHREIBER.

Witnesses:

ALBERT VIEwEs, OTTO REIoHoLD.

